Table 1: Effective Cutting Diameter (ECD)

  Depth of Cut (DOC)
Insert Diameter   .005 .010 .015 .025 .035 .050 .100 .125 .150 .200 .250
.250 .070 .098 .119 .150 .173 .200 .245 .250      
.375 .086 .121 .147 .187 .218 .255 .332 .354 .367 .374  
.500 .099 .140 .171 .218 .255 .300 .400 .433 .458 .490 .500
.625 .111 .157 .191 .245 .287 .339 .458 .500 .534 .583 .612
.750 .122 .172 .210 .269 .316 .374 .510 .559 .600 .663 .707
1.000 .141 .199 .243 .312 .368 .436 .600 .661 .714 .800 .866
1.250 .158 .223 .272 .350 .412 .490 .678 .750 .812 .917 1.000

  1. Select diameter of tool to be used.
  2. Determine Depth of Cut (DOC) to be used.
  3. Refer to Figure 1 and Table 1 to find the Effective Cutting Diameter (ECD).
  4. Refer to the Ball Nose Feed and Speed chart (PDF) to select the surface footage to be used (SFM).
  5. Calculate RPM using the ECD and SFM. (SFM x 3.82 / ECD = RPM)
  6. Refer to Table 2 to determine Feed Rate Adjustment (FRA).
  7. Refer to the Feed and Speed chart (PDF) to select Feed per Tooth (FPT). Calculate Inches per Minute (IPM). (RPM x FPT x FRA = IPM)
Figure 1 - Ball Nose Effective Cutting Diameter

Table 2: Feed Rate Adjustment (FRA)

  Insert Diameter
Depth of Cut (DOC)   1/4" 5/16" 3/8" 1/2" 5/8" 3/4" 1" 1-1/4"
.005 3.6 4.0 4.4 5.0 5.6 6.1 7.1 7.9
.010 2.6 2.8 3.1 3.6 4.0 4.4 5.0 5.6
.015 2.1 2.3 2.6 2.9 3.3 3.6 4.1 4.6
.020 1.8 2.0 2.2 2.6 2.8 3.1 3.6 4.0
.025 1.7 1.8 2.0 2.3 2.6 2.8 3.2 3.6
.050 1.2 1.4 1.5 1.7 1.8 2.0 2.3 2.6
.075 1.1 1.2 1.2 1.4 1.5 1.7 1.9 2.1
.100   1.1 1.1 1.2 1.4 1.5 1.7 1.8
.125     1.1 1.2 1.3 1.3 1.5 1.7
.150       1.1 1.2 1.3 1.4 1.5
.175         1.1 1.2 1.3 1.4
.200           1.1 1.3 1.4
.250             1.2 1.2
.300             1.1 1.2
.400               1.1

Use multiple above to calculate adjusted feed rate.